Nuclear weapons test? The latest test treaty just expired.
Edit: There are two TFRs, one in El Paso and one right next to it in the mountains: https://tfr.faa.gov/tfr3/?page=detail_6_2234
Probably just closing the airspace for the space alien emissary.
Wouldn’t the Nevada Test Site be much better for this? Huge, government controlled, no major airports or cities, and moreover, already used for this sort of thing.
This was my thought as well given the length of time of the closure.
3.6 roentgen you say?
I think not; it's not somewhere you can conduct a nuclear test without starting a war with Mexico. However it is interesting to look at the TFR area in Google maps; it looks just like a nuclear test site, but the craters are natural volcanoes.